Sample response: t represents time, which is the input of the function, so we know that 10 is the time in minutes. H(t) represents the altitude, which is the output of the function after time, t. So, we need to substitute 10 into 210 – 15t in place of t. Simplifying 210 – 15(10), we get that 60 is the altitude in feet. So, after 10 minutes, the hot air balloon is at 60 feet. What did you include in your response? check all that apply. T represents time, which is the input of the function. H(t) represents the altitude, which is the output of the function. After 10 minutes, the hot air balloon is at 60 feet.